Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) (Commodity [Member])	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2011
IPL [Member] | Electricity [Member]
Notional Unit Amount Of Derivatives			789,000	488,000	1,277,000
WPL [Member] | Electricity [Member]
Notional Unit Amount Of Derivatives		204,000	859,000	946,000	2,009,000
Electricity [Member]
Notional Unit Amount Of Derivatives		204,000	1,648,000	1,434,000	3,286,000
IPL [Member] | FTRs [Member]
Notional Unit Amount Of Derivatives			14,000	17,000	31,000
WPL [Member] | FTRs [Member]
Notional Unit Amount Of Derivatives			9,000	13,000	22,000
FTRs [Member]
Notional Unit Amount Of Derivatives			23,000	30,000	53,000
IPL [Member] | Natural Gas [Member]
Notional Unit Amount Of Derivatives	225,000	2,100,000	8,232,000	23,055,000	33,612,000
WPL [Member] | Natural Gas [Member]
Notional Unit Amount Of Derivatives	225,000	2,573,000	11,580,000	10,449,000	24,827,000
Natural Gas [Member]
Notional Unit Amount Of Derivatives	450,000	4,673,000	19,812,000	33,582,000	58,517,000